The present invention relates to a feedthrough for an optical fiber or fibers provided in an optical submarine cable repeater.
An optical submarine cable using optical fibers is laid on the bottom of the sea sometimes as deep as several thousand meters, and hence is exposed to a hydraulic pressure of several hundred atmospheres. A repeater housing for use under such severe conditions is made of material which is highly resistant to corrosion by sea water, such as stainless steel, beryllium copper alloy or the like. The optical fiber is introduced, through a feedthrough mounted on an end plate of the pressure-tight repeater housing, into optical repeater circuitry housed in the repeater housing. Accordingly, in order to introduce the optical fiber and a power-supplying feeder into the pressure-tight repeater housing under the hydraulic pressure of several hundred atmospheres, a highly reliable feedthrough is required which is sufficiently sturdy to withstand such high hydraulic pressures, fully insulated electrically from sea water, air-tight and stably usable for a long period of time.
As described above, the most important problems of the long-distance optical submarine cable system are to maintain its life time of more than 20 years and to definitely establish a method for guaranteeing the long-term reliability. The submarine cable system potentials cannot be realized unless its reliability is guaranteed.